1. Field of the Invention
The present invention relates to a wafer pod gas filling system, particularly to a wafer pod gas filling system having a standard mechanical interface (SMIF).
2. Description of Related Art
Conventionally, during production of semiconductor wafers, if in a pod for transport or temporary storage oxygen and moisture are contained, the wafer surface easily and often undergoes undesired reactions, e.g., a native oxide film develops. Since today's semiconductor wafers have an increasingly refined structure with a high degree of integration, the wafer surfaces become more and more sensitive to the environment thereof. Particularly for critical fabrication steps, like thermal processing, chemical vapor deposition, or sputtering, these undesired reactions reduce product quality and often cause electrical device failure.
Therefore, for transport or temporary storage of wafers in a pod, a gas filling system is needed, substituting an inert gas, like nitrogen or helium for air, so as to maintain required production quality.
Conventional gas filling systems, however, have several disadvantages:
1. A conventional wafer pod gas filling system is not adaptable to a mechanical interface, thus standard wafer pods cannot be connected. A latch mechanism cannot be locked to the wafer pod cover, so that the wafer pod easily shakes when filled with gas.
2. The gas filling nozzle and the gas outlet are located on the same side, therefore during filling gas escapes laterally, resulting in waste of gas, inefficient filling and high gas consumption of over 70 liters per minute. Then pressure exceeds 125 psi, there is also an operational risk.
3. A conventional wafer pod gas filling system has no built-in inert gas supply unit, only an inlet and an outlet. Therefore, filling is slow, and there is no way to adjust pressure and flow.
4. A conventional wafer pod gas filling system has a single nozzle which is horizontally oriented. Thus gas flows out rapidly with a large noise, causing vibrations of the wafer in the pod.
Conventional wafer pod gas filling systems therefore have several shortcomings.